A pair of teenage girls say they witnessed a man indecently exposing himself in broad daylight in Hemel Hempstead earlier this week.
The alleged incident took place in Fletcher Way, Highfield, at around 3.45pm on Wednesday.
Police are searching for the man, who is described as white, aged between 35 and 40 and of stocky build.
According to the witnesses, who walked past the pervert before he got into a white Ford van and drove past them, he had short, dark brown curly hair and was wearing blue workman-style clothes.
Anyone with information about the incident is asked to call police on the non-emergency number 101, citing reference D1/14/2594.